Re: Cayman Aggressor Experiences?

Nitrox is for relatively shallow dives. Depending on the percentage
oxygen, you could go to 100 feet, but 50-80 is more appropriate. In
places like Cozumel where there's the potential for some 100+ first
dives, most people do air on the first dive because you can get into
very distressing situations in a down current and nitrox on the second
(if they are nitrox certified).

If you have a local dive shop, go and buy the PADI (or whatever)
nitrox/enriched air book to get an idea of what this is all about.
There are some additional issues with nitrox that simplify to maximum
depth of less than 130.

I'm 55 and find nitrox a bit less tiring. Some say its all
psychological, others say it is easier to off gas.

"DrYak" <DrYak@nospam.com> wrote in message
news:7wLCc.13281$WI2.6160@lakeread05...

> Nitrox is for relatively shallow dives. Depending on the percentage
> oxygen, you could go to 100 feet, but 50-80 is more appropriate. In
> places like Cozumel where there's the potential for some 100+ first
> dives, most people do air on the first dive because you can get into
> very distressing situations in a down current and nitrox on the second
> (if they are nitrox certified).

?

> If you have a local dive shop, go and buy the PADI (or whatever)
> nitrox/enriched air book to get an idea of what this is all about.
> There are some additional issues with nitrox that simplify to maximum
> depth of less than 130.

?

When I dive to 140' (the bottom of the wall at Captain Don's Habitat, for
instance, or Farnsworth Banks), I routinely dive a 28% mix which keeps me at
about 1.45 and gives me a lot more bottom time than air would. Not only
that, but (allegedly) narcosis is reduced. You're not one of those deep air
types, are you?

"Greg Mossman" <mossman@qnet.com> wrote in message
news:40db9503$0$106$6c56adcd@news.qnet.com...
>
> When I dive to 140' (the bottom of the wall at Captain Don's Habitat, for
> instance, or Farnsworth Banks), I routinely dive a 28% mix which keeps me
at
> about 1.45 and gives me a lot more bottom time than air would. Not only
> that, but (allegedly) narcosis is reduced. You're not one of those deep
air
> types, are you?

Perhaps Dr. Yak is worried about not having a hard bottom and the potential
for diver error with more standard mixes of 36 and 32%?

"chilly" <slarson@shaw.canada> wrote in message
news:FLPCc.893836$Ig.778642@pd7tw2no...

> Perhaps Dr. Yak is worried about not having a hard bottom and the
potential
> for diver error with more standard mixes of 36 and 32%?

Why would he worry about that? Anyone with a modicum of buoyancy control
isn't worried about the hard bottom. The possbility of downcurrents in
Cozumel is an issue, but not really. It takes more than a couple seconds at
an excessive ppO2 to start convulsing - the blood needs time to circulate
from the lungs, after all. Still, Dr. Yak could limit his nitrox use to
"relatively shallow dives" in areas known for downcurrents. It certainly
doesn't preclude the use of nitrox on deeper hard bottoms or in areas where
downcurrents are rarely reported.

"Standard" mixes of 32 and 36 mean nothing to someone filling nitrox with
anything other than banked nitrox. My standard mixes are usually something
around 28-30% if I want to go "relatively deep" or something around 40-45%
if I'm hanging with Dr. Yak in the shallows.

To keep on topic, the Aggressors probably try for 32% which means they're
pumping anywhere from 30-33%, safe and very beneficial to 100' - that's
still a far cry from Dr. Yak's "50-80 is more appropriate".

"Greg Mossman" <mossman@qnet.com> wrote in message news:<40dc3def$0$105$6c56adcd@news.qnet.com>...

> "Standard" mixes of 32 and 36 mean nothing to someone filling nitrox with
> anything other than banked nitrox. My standard mixes are usually something
> around 28-30% if I want to go "relatively deep" or something around 40-45%
> if I'm hanging with Dr. Yak in the shallows.

And none of that means anything unless you take into consideration the
time of EXPOSURE, the PPO2 level, the MOD, and other things you are
supposed to have learned in your EAN course, and much the
PADI course doesn't even teach! SSI (Bret Gilliam's book) offers a
much better basis (I studeied it because I was on the witness stand
AGAINST Bret in the Uwatec Nitrox computer case <G>). I had already
been PADI Nitrox certified.

Neither courses are worth a damn if you really want to understand EAN
and how to dive with Nitrox properly.

Try read up on NOAA stuff about EXPOSURE times. The Nitrox equivalent
of AIR exposure times that are safe in PRACTICE. The 130 fsw max for
air is for the uneducated pedants. For SHORT exposure times, it's
perfectly safe to dive to 200 feet on air (unless you are one of
those who get narcosis easily at that and much shallower depths).


> To keep on topic, the Aggressors probably try for 32% which means they're
> pumping anywhere from 30-33%, safe and very beneficial to 100'

Also "safe and benefcial" to 130' and more if you use 1.6 as your PPO2
level of reference, and quite safe for short times of exposure below that.

- that's still a far cry from Dr. Yak's "50-80 is more appropriate".


I have an andedotal story to tell about my Cayman Aggressor trip in
1999. I was diving with my ORCA computer on air, and the Uwatec
Nitrox PRO on EAN, and was laughing at my friend "Crusty" for diving
with a Cochran computer (actual that one was ok -- because Cochran
had already introduced tweaks to UNTWEAK the errors he had programmed
in his privious models).

At any rate, Crusty was quick to point out that My Uwatec Nitrox
computer DROPPED DEAD (locked out) on the last day (about Dive 23
of that trip), while his Cochran computer was still alive.

It was then that I had to explain to him the reason the Uwatec Nitrox
PRO locked out was that 10 dives BEFORE I had taken it to a 196 fsw
dive (on AIR) while forgetting to reset the EAN 32 to EAN 21.

Not that I would want to dive to 196 fsw on EAN32, but the little
error in forgetting to reset the EAN to 21 when I made that deep
AIR <not EAN32) bounce (at the Great Wall in Little Cayman) was
that it showed that as CONSERVATIVE the Uwatec Nitrox PRO was, it
"survived" that dive, and the next 9 dives, until it finally caught
up 10 dives later and decided it had better play dead.

But the bottom line is that apparently Buehmann's model thought it
was "safe" for someone to have done that dive on EAN32 to a max
depth of 196 fsw! Buehmann was right (if you take into consideration
the TIME OF EXPOSURE) of that dive at various depths.

-- Bob.














My anecdotal story on this is the time I dived to 196 fsw on one of
my Cayman Aggressor dives in 1998, on AIR. A short bounce as I had
done more times than I could count in Cozumel.

Greg Mossman wrote:
> "DrYak" <DrYak@nospam.com> wrote in message
> news:7wLCc.13281$WI2.6160@lakeread05...
>
>
>>Nitrox is for relatively shallow dives. Depending on the percentage
>>oxygen, you could go to 100 feet, but 50-80 is more appropriate. In
>>places like Cozumel where there's the potential for some 100+ first
>>dives, most people do air on the first dive because you can get into
>>very distressing situations in a down current and nitrox on the second
>>(if they are nitrox certified).
>
>
> ?
>
>
>>If you have a local dive shop, go and buy the PADI (or whatever)
>>nitrox/enriched air book to get an idea of what this is all about.
>>There are some additional issues with nitrox that simplify to maximum
>>depth of less than 130.
>
>
> ?
>
> When I dive to 140' (the bottom of the wall at Captain Don's Habitat, for
> instance, or Farnsworth Banks), I routinely dive a 28% mix which keeps me at
> about 1.45 and gives me a lot more bottom time than air would. Not only
> that, but (allegedly) narcosis is reduced. You're not one of those deep air
> types, are you?
>
>
I agree that diving with 28% would be helpful, but lots/most places seem
to offer only 32 or 36%. The potential for a down current on some of
the walls at Cozumel is real enough so I'll pass on the nitrox for that
first dive. The bottom there can be several hundred feet so I don't
want to combine my 32%, 160 feet, and the stress of getting back under
control. Don't get me wrong on this stress issue. I'm not going to
panic, but I'll probably be breathing a little faster than normal. I
just don't want to take the risk. Also, I don't have a regular dive
buddy, so I'm taking luck of the draw.

DrYak <DrYak@nospam.com> wrote in message news:<t22Dc.16133$WI2.11881@lakeread05>...

> The potential for a down current on some of
> the walls at Cozumel is real enough so I'll pass on the nitrox for that
> first dive.

There are NO downcurrents in Cozumel walls. Trust me.

There was an incidence in 1992, discussed at length in rec.scuba, in
which a diver was pulled down by a "vortex" near the Santa Rosa wall,
but a vortex (circular motion caused by rare weather conditions) are
NOT downcurrents.

THe person who was pulled down by the vortex did leave some brown
spots insides his wetsuit. BUt that was about the extent of the
damage.


The only thing that ever pulled me below 150' in Cozumel is when my
buoyancy was deliberately made negative to descend.

-- Bob.

Bob,

When I was in Cozumel in 2001, one of my dive buddies told me he had
been in a down current and got out at 150-160 feet. I wasn't diving
with him that day, but I trust him. In any case, doing nitrox on those
first dives is not like to get you any extra bottom time because most of
the dives are run by the DM, not your computer. The surface interval
won't be shorter because you dive nitrox. So I'll dive it on the second
dive.

Dr Y.

Reef Fish wrote:

> DrYak <DrYak@nospam.com> wrote in message news:<t22Dc.16133$WI2.11881@lakeread05>...
>
>
>>The potential for a down current on some of
>>the walls at Cozumel is real enough so I'll pass on the nitrox for that
>>first dive.
>
>
> There are NO downcurrents in Cozumel walls. Trust me.
>
> There was an incidence in 1992, discussed at length in rec.scuba, in
> which a diver was pulled down by a "vortex" near the Santa Rosa wall,
> but a vortex (circular motion caused by rare weather conditions) are
> NOT downcurrents.
>
> THe person who was pulled down by the vortex did leave some brown
> spots insides his wetsuit. BUt that was about the extent of the
> damage.
>
>
> The only thing that ever pulled me below 150' in Cozumel is when my
> buoyancy was deliberately made negative to descend.
>
> -- Bob.

DrYak <DrYak@nospam.com> wrote in message news:<RVHDc.17445$WI2.9842@lakeread05>...
> Bob,
>
> When I was in Cozumel in 2001, one of my dive buddies told me he had
> been in a down current and got out at 150-160 feet. I wasn't diving
> with him that day, but I trust him.

I was most like one of those rare "vortex" conditions that I memntioned
in my post. I repeat -- it's NOT a "down current". I've done a total
of nearly 1200 dives in Cozumel, on every divable site multiples of
times and have talked to more DMs in Cuzumel than most people know --
the conclusion is all the same: there are NO down currents in Cozumel.


> In any case, doing nitrox on those
> first dives is not like to get you any extra bottom time because most of
> the dives are run by the DM, not your computer.

Wrong on several counts.

1. On nearly all Cozumel dives, especially in the depth ranges you were
talking about, diving nitrox does NOT necessarily give you any more
bottom time (and definitely not more on the 2nd <shallower> dive".
It gives you LESS nitrogen loading.

2. For many people, the air consumption on nitrox is indistinguable
from that of air <see also (1) above>.

3. Some dive shops (and DMs) let you dive what your computer AND your
tank of air/EAN will last.

It appears that you're not very well informed about nitrox, and you
seem to be wanting to dive nitrox for all the WRONG reasons.


> The surface interval won't be shorter because you dive nitrox.

Why not? If your intake of nitrogen is LESS than that of air, then
doesn't it follow that you SI for "off gasing" will be less (or the
time REQUIRED)?


> So I'll dive it on the second dive.

Do you know why?
>
> Dr Y.

-- Bob. Dr. L.

>
> Reef Fish wrote:
>
> > DrYak <DrYak@nospam.com> wrote in message news:<t22Dc.16133$WI2.11881@lakeread05>...
> >
> >
> >>The potential for a down current on some of
> >>the walls at Cozumel is real enough so I'll pass on the nitrox for that
> >>first dive.
> >
> >
> > There are NO downcurrents in Cozumel walls. Trust me.
> >
> > There was an incidence in 1992, discussed at length in rec.scuba, in
> > which a diver was pulled down by a "vortex" near the Santa Rosa wall,
> > but a vortex (circular motion caused by rare weather conditions) are
> > NOT downcurrents.
> >
> > THe person who was pulled down by the vortex did leave some brown
> > spots insides his wetsuit. BUt that was about the extent of the
> > damage.
> >
> >
> > The only thing that ever pulled me below 150' in Cozumel is when my
> > buoyancy was deliberately made negative to descend.
> >
> > -- Bob.

Reef Fish wrote:
> DrYak <DrYak@nospam.com> wrote in message news:<RVHDc.17445$WI2.9842@lakeread05>...
>
>>Bob,
>>
>>When I was in Cozumel in 2001, one of my dive buddies told me he had
>>been in a down current and got out at 150-160 feet. I wasn't diving
>>with him that day, but I trust him.
>
>
> I was most like one of those rare "vortex" conditions that I memntioned
> in my post. I repeat -- it's NOT a "down current". I've done a total
> of nearly 1200 dives in Cozumel, on every divable site multiples of
> times and have talked to more DMs in Cuzumel than most people know --
> the conclusion is all the same: there are NO down currents in Cozumel.
>
>
>
So the vortex swept him down. The end result is the same:
unanticipated depths that were not planned for with the MOD of the
nitrox mix.

>>In any case, doing nitrox on those
>>first dives is not like to get you any extra bottom time because most of
>>the dives are run by the DM, not your computer.
>
>
> Wrong on several counts.
>
> 1. On nearly all Cozumel dives, especially in the depth ranges you were
> talking about, diving nitrox does NOT necessarily give you any more
> bottom time (and definitely not more on the 2nd <shallower> dive".
> It gives you LESS nitrogen loading.
>
Where can you get custom mixes of say 28 percent oxygen in Coz? All
I've been offered is 32.


> 2. For many people, the air consumption on nitrox is indistinguable
> from that of air <see also (1) above>.
>
I know that air consumption is the same with air and nitrox.

> 3. Some dive shops (and DMs) let you dive what your computer AND your
> tank of air/EAN will last.
>

Got any recommendations for dive shops that will let me dive my computer
even if the other divers are back on the boat?

> It appears that you're not very well informed about nitrox, and you
> seem to be wanting to dive nitrox for all the WRONG reasons.
>
>
>
>>The surface interval won't be shorter because you dive nitrox.
>
>
> Why not? If your intake of nitrogen is LESS than that of air, then
> doesn't it follow that you SI for "off gasing" will be less (or the
> time REQUIRED)?
>
Because if I'm the only one diving nitrox, we're not getting back into
the water until my air breathing friends have off gassed enough. I'll
just be a little safer then them. Now if we're all diving nitrox, then
we can take advantage of a shorter surface interval, but one or two
divers on even a six pack and we're going to get some more sun.
>
>
>>So I'll dive it on the second dive.
>
>
> Do you know why?
>
>>Dr Y.
>
>
> -- Bob. Dr. L.
>
>
>>Reef Fish wrote:
>>
>>
>>>DrYak <DrYak@nospam.com> wrote in message news:<t22Dc.16133$WI2.11881@lakeread05>...
>>>
>>>
>>>
>>>>The potential for a down current on some of
>>>>the walls at Cozumel is real enough so I'll pass on the nitrox for that
>>>>first dive.
>>>
>>>
>>>There are NO downcurrents in Cozumel walls. Trust me.
>>>
>>>There was an incidence in 1992, discussed at length in rec.scuba, in
>>>which a diver was pulled down by a "vortex" near the Santa Rosa wall,
>>>but a vortex (circular motion caused by rare weather conditions) are
>>>NOT downcurrents.
>>>
>>>THe person who was pulled down by the vortex did leave some brown
>>>spots insides his wetsuit. BUt that was about the extent of the
>>>damage.
>>>
>>>
>>>The only thing that ever pulled me below 150' in Cozumel is when my
>>>buoyancy was deliberately made negative to descend.
>>>
>>>-- Bob.